1. Field of the Invention
This invention relates to a process for the production of semiconductor devices by which a liquid phase epitaxial growth can be attained without meltback in the channelled substrate since the channelled substrate includes a semiconductor layer containing aluminum.
2. Description of the Prior Art
With the development of optical devices, a liquid phase epitaxial growth technique using group III-V semiconductor compounds (especially, Al.sub.x Ga.sub.1-x As) has been widely applied to the production of semiconductor laser devices, light emitting diodes, etc. These devices are produced by the liquid phase epitaxial growth of crystalline layers on the channelled substrate resulting in a variety of structures.
However, during the liquid phase epitaxial growth of crystalline layers on the channelled substrate, each of the shoulder portions of both sides of the channel undergoes meltback resulting in a rounded shape. For example, FIGS. 4(a) and 4(b) show a conventional production process of semiconductor laser devices, FIG. 4(a) showing a sectional view of the channelled substrate and FIG. 4(b) showing a sectional view of the current blocking wafer. On a p-GaAs substrate 1, an n-GaAs current blocking layer 2 is formed by liquid phase epitaxy, molecular beam epitaxy, metal-organic-chemical vapor deposition, etc., followed by the formation of a channel on the surface of the substrate 1 by the use of photolithography and an etching technique (FIG. 4(a)). Then, on the resulting channelled substrate 21, a p-Al.sub.x Ga.sub.1-x As cladding layer 3, an Al.sub.y Ga.sub.1-y As active layer 4, an n-Al.sub.x Ga.sub.1-x As cladding layer 5 and an n.sup.+ -GaAs cap layer 6 are successively formed by liquid phase epitaxy (wherein, 0.ltoreq.Y.ltoreq.X.ltoreq.1) (FIG. 4(b)). During the successive growth of the crystalline layers on the channelled substrate 21, the shoulder portions of the channel undergo meltback into a crystal growth solution resulting in a rounded shape, so that the width of the channel expands to a certain extent, causing changes in the width of an electric current injection region and/or an optical waveguide, and resulting in a great variability in the device characteristics. In order to produce devices having uniform characteristics, meltback in the channel of the substrate must be prevented during the successive growth of the crystalline layers on the channelled substrate.